
/**
 * 计算距离
 */
export function getDistance(lat1, lng1, lat2, lng2, decimal) {
  decimal = decimal || 2;
  lat1 = lat1 || 0;
  lng1 = lng1 || 0;
  lat2 = lat2 || 0;
  lng2 = lng2 || 0;
  let radLat1 = lat1 * Math.PI / 180.0;
  let radLat2 = lat2 * Math.PI / 180.0;
  let a = radLat1 - radLat2;
  let b = lng1 * Math.PI / 180.0 - lng2 * Math.PI / 180.0;
  let s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2) +
    Math.cos(radLat1) * Math.cos(radLat2) * Math.pow(Math.sin(b / 2), 2)));
  s = s * 6378.137;// EARTH_RADIUS;
  s = Math.round(s * 10000) / 10000;
  return parseFloat(s.toFixed(decimal));
}